package tree;

import hash.Queue;

import java.util.NoSuchElementException;

/**
 * @description: 二叉红黑查找树
 * @author: zp
 * @date: 2021/12/4 17:12
 * @param: null
 * @return:
 */
public class RedBlackBST<Key extends Comparable<Key>, Value> {

    private static final boolean RED = true;
    private static final boolean BLACK = false;

    private Node root;     // root of the BST

    // BST helper node data type
    private class Node {
        private Key key;           // key
        private Value val;         // associated data
        private Node left, right;  // links to left and right subtrees
        private boolean color;     // color of parent link
        private int size;          // subtree count

        public Node(Key key, Value val, boolean color, int size) {
            this.key = key;
            this.val = val;
            this.color = color;
            this.size = size;
        }
    }

    /**
     * Initializes an empty symbol table.
     */
    public RedBlackBST() {
    }

    /***************************************************************************
     *  Node helper methods.
     ***************************************************************************/
    //判断节点是否为红色
    private boolean isRed(Node x) {
        if (x == null) {
            return false;
        }
        return x.color == RED;
    }

    // 获取节点大小
    private int size(Node x) {
        if (x == null) {
            return 0;
        }
        return x.size;
    }


    /**
     * Returns the number of key-value pairs in this symbol table.
     *
     * @return the number of key-value pairs in this symbol table
     */
    public int size() {
        return size(root);
    }

    /**
     * 查看树是否为空
     *
     * @return {@code true} if this symbol table is empty and {@code false} otherwise
     */
    public boolean isEmpty() {
        return root == null;
    }


    /***************************************************************************
     *  Standard BST search.
     ***************************************************************************/

    /**
     * 根据可以值返回元素
     *
     * @param key the key
     * @return the value associated with the given key if the key is in the symbol table
     * and {@code null} if the key is not in the symbol table
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public Value get(Key key) {
        if (key == null) {
            throw new IllegalArgumentException("argument to get() is null");
        }
        return get(root, key);
    }

    // value associated with the given key in subtree rooted at x; null if no such key
    private Value get(Node x, Key key) {
        while (x != null) {
            int cmp = key.compareTo(x.key);
            if (cmp < 0) {
                x = x.left;
            } else if
            (cmp > 0) {
                x = x.right;
            } else {
                return x.val;
            }
        }
        return null;
    }

    /**
     * 判断树中是否存在key为这个的元素
     *
     * @param key the key
     * @return {@code true} if this symbol table contains {@code key} and
     * {@code false} otherwise
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public boolean contains(Key key) {
        return get(key) != null;
    }

    /***************************************************************************
     *  Red-black tree insertion.
     ***************************************************************************/

    /**
     * 添加元素
     *
     * @param key the key
     * @param val the value
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public void put(Key key, Value val) {
        if (key == null) {
            throw new IllegalArgumentException("first argument to put() is null");
        }
        if (val == null) {
            delete(key);
            return;
        }

        root = put(root, key, val);
        root.color = BLACK;
        // assert check();
    }

    // insert the key-value pair in the subtree rooted at h
    private Node put(Node h, Key key, Value
            val) {
        if (h == null) {
            return new Node(key, val, RED, 1);
        }

        int cmp = key.compareTo(h.key);
        if (cmp < 0) {
            h.left = put(h.left, key, val);
        } else if (cmp > 0) {
            h.right = put(h.right, key, val);
        } else {
            h.val = val;
        }

        // 如果右边为红色 左边为黑色 左旋该节点
        if (isRed(h.right) && !isRed(h.left)) {
            h = rotateLeft(h);
        }
        // 如果元素的左节点为红色 左节点的左节点还是为红色 右旋该节点
        if (isRed(h.left) && isRed(h.left.left)) {
            h = rotateRight(h);
        }
        //如果改节点左右都为红色节点 该节点的颜色取反
        if (isRed(h.left) && isRed(h.right)) {
            flipColors(h);
        }
        h.size = size(h.left) + size(h.right) + 1;

        return h;
    }

    /***************************************************************************
     *  Red-black tree deletion.
     ***************************************************************************/

    /**
     * 删除二叉树当中最小元素
     *
     * @throws NoSuchElementException if the symbol table is empty
     */
    public void deleteMin() {
        if (isEmpty()) {
            throw new NoSuchElementException("BST underflow");
        }

        // if both children of root are black, set root to red
        if (!isRed(root.left) && !isRed(root.right)) {
            root.color = RED;
        }

        root = deleteMin(root);
        if (!isEmpty()) {
            root.color = BLACK;
        }
        // assert check();
    }

    // delete the key-value pair with the minimum key rooted at h
    private Node deleteMin(Node h) {
        if (h.left == null) {
            return null;
        }

        if (!isRed(h.left) && !isRed(h.left.left)) {
            h = moveRedLeft(h);
        }

        h.left = deleteMin(h.left);
        {
            return balance(h);
        }
    }


    /**
     * 删除二叉树当中最大元素
     *
     * @throws NoSuchElementException if the symbol table is empty
     */
    public void deleteMax() {
        if (isEmpty()) throw new NoSuchElementException("BST underflow");

        // if both children of root are black, set root to red
        if (!isRed(root.left) && !isRed(root.right)) {
            root.color = RED;
        }

        root = deleteMax(root);
        if (!isEmpty()) {
            root.color = BLACK;
        }
        // assert check();
    }

    // delete the key-value pair with the maximum key rooted at h
    private Node deleteMax(Node h) {
        if (isRed(h.left)) {
            h = rotateRight(h);
        }

        if (h.right == null) {
            return null;
        }

        if (!isRed(h.right) && !isRed(h.right.left)) {
            h = moveRedRight(h);
        }

        h.right = deleteMax(h.right);

        return balance(h);
    }

    /**
     * 删除key为传入的值
     *
     * @param key the key
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public void delete(Key key) {
        if (key == null) {
            throw new IllegalArgumentException("argument to delete() is null");
        }
        if (!contains(key)) {
            return;
        }

        // if both children of root are black, set root to red
        if (!isRed(root.left) && !isRed(root.right)) {
            root.color = RED;
        }

        root = delete(root, key);
        if (!isEmpty()) {
            root.color = BLACK;
        }
        // assert check();
    }

    // delete the key-value pair with the given key rooted at h
    private Node delete(Node h, Key key) {
        // assert get(h, key) != null;

        if (key.compareTo(h.key) < 0) {
            if (!isRed(h.left) && !isRed(h.left.left)) {
                h = moveRedLeft(h);
            }
            h.left = delete(h.left, key);
        } else {
            if (isRed(h.left)) {
                h = rotateRight(h);
            }
            if (key.compareTo(h.key) == 0 && (h.right == null)) {
                return null;
            }
            if (!isRed(h.right) && !isRed(h.right.left)) {
                h = moveRedRight(h);
            }
            if (key.compareTo(h.key) == 0) {
                Node x = min(h.right);
                h.key = x.key;
                h.val = x.val;
                // h.val = get(h.right, min(h.right).key);
                // h.key = min(h.right).key;
                h.right = deleteMin(h.right);
            } else {
                h.right = delete(h.right, key);
            }
        }
        return balance(h);
    }

    /***************************************************************************
     *  Red-black tree helper functions.
     ***************************************************************************/

    // 右旋
    private Node rotateRight(Node h) {
        assert (h != null) && isRed(h.left);
        // assert (h != null) && isRed(h.left) &&  !isRed(h.right);  // for insertion only
        Node x = h.left;
        h.left = x.right;
        x.right = h;
        x.color = x.right.color;
        x.right.color = RED;
        x.size = h.size;
        h.size = size(h.left) + size(h.right) + 1;
        return x;
    }

    // 左旋
    private Node rotateLeft(Node h) {
        assert (h != null) && isRed(h.right);
        // assert (h != null) && isRed(h.right) && !isRed(h.left);  // for insertion only
        Node x = h.right;
        h.right = x.left;
        x.left = h;
        x.color = x.left.color;
        x.left.color = RED;
        x.size = h.size;
        h.size = size(h.left) + size(h.right) + 1;
        return x;
    }

    // 颜色取反
    private void flipColors(Node h) {
        // h must have opposite color of its two children
        // assert (h != null) && (h.left != null) && (h.right != null);
        // assert (!isRed(h) &&  isRed(h.left) &&  isRed(h.right))
        //    || (isRed(h)  && !isRed(h.left) && !isRed(h.right));
        h.color = !h.color;
        h.left.color = !h.left.color;
        h.right.color = !h.right.color;
    }

    //删除红色左元素
    private Node moveRedLeft(Node h) {
        // assert (h != null);
        // assert isRed(h) && !isRed(h.left) && !isRed(h.left.left);

        flipColors(h);
        if (isRed(h.right.left)) {
            h.right = rotateRight(h.right);
            h = rotateLeft(h);
            flipColors(h);
        }
        return h;
    }

    //删除红色右元素
    private Node moveRedRight(Node h) {
        // assert (h != null);
        // assert isRed(h) && !isRed(h.right) && !isRed(h.right.left);
        flipColors(h);
        if (isRed(h.left.left)) {
            h = rotateRight(h);
            flipColors(h);
        }
        return h;
    }

    // 把跟改之后的树还原成二叉红黑查找树
    private Node balance(Node h) {
        // assert (h != null);

        if (isRed(h.right) && !isRed(h.left)) h = rotateLeft(h);
        if (isRed(h.left) && isRed(h.left.left)) {
            h = rotateRight(h);
        }
        if (isRed(h.left) && isRed(h.right)) {
            flipColors(h);
        }

        h.size = size(h.left) + size(h.right) + 1;
        return h;
    }


    /***************************************************************************
     *  Utility functions.
     ***************************************************************************/

    /**
     * 获取树的高度
     *
     * @return the height of the BST (a 1-node tree has height 0)
     */
    public int height() {
        return height(root);
    }

    private int height(Node x) {
        if (x == null) {
            return -1;
        }
        return 1 + Math.max(height(x.left), height(x.right));
    }

    /***************************************************************************
     *  Ordered symbol table methods.
     ***************************************************************************/

    /**
     * 获取最小元素
     *
     * @return the smallest key in the symbol table
     * @throws NoSuchElementException if the symbol table is empty
     */
    public Key min() {
        if (isEmpty()) {
            throw new NoSuchElementException("calls min() with empty symbol table");
        }
        return min(root).key;
    }

    // the smallest key in subtree rooted at x; null if no such key
    private Node min(Node x) {
        // assert x != null;
        if (x.left == null) {
            return x;
        } else {
            return min(x.left);
        }
    }

    /**
     * 获取最大元素
     *
     * @return the largest key in the symbol table
     * @throws NoSuchElementException if the symbol table is empty
     */
    public Key max() {
        if (isEmpty()) {
            throw new NoSuchElementException("calls max() with empty symbol table");
        }
        return max(root).key;
    }

    // the largest key in the subtree rooted at x; null if no such key
    private Node max(Node x) {
        // assert x != null;
        if (x.right == null) {
            return x;
        } else {
            return max(x.right);
        }
    }


    /**
     * Returns the largest key in the symbol table less than or equal to {@code key}.
     *
     * @param key the key
     * @return the largest key in the symbol table less than or equal to {@code key}
     * @throws NoSuchElementException   if there is no such key
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public Key floor(Key key) {
        if (key == null) {
            throw new IllegalArgumentException("argument to floor() is null");
        }
        if (isEmpty()) {
            throw new NoSuchElementException("calls floor() with empty symbol table");
        }
        Node x = floor(root, key);
        if (x == null) {
            throw new NoSuchElementException("argument to floor() is too small");
        } else {
            return x.key;
        }
    }

    // the largest key in the subtree rooted at x less than or equal to the given key
    private Node floor(Node x, Key key) {
        if (x == null) {
            return null;
        }
        int cmp = key.compareTo(x.key);
        if (cmp == 0) {
            return x;
        }
        if (cmp < 0) {
            return floor(x.left, key);
        }
        Node t = floor(x.right, key);
        if (t != null) {
            return t;
        } else {
            return x;
        }
    }

    /**
     * Returns the smallest key in the symbol table greater than or equal to {@code key}.
     *
     * @param key the key
     * @return the smallest key in the symbol table greater than or equal to {@code key}
     * @throws NoSuchElementException   if there is no such key
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public Key ceiling(Key key) {
        if (key == null) {
            throw new IllegalArgumentException("argument to ceiling() is null");
        }
        if (isEmpty()) {
            throw new NoSuchElementException("calls ceiling() with empty symbol table");
        }
        Node x = ceiling(root, key);
        if (x == null) {
            throw new NoSuchElementException("argument to ceiling() is too small");
        } else {
            return x.key;
        }
    }

    // the smallest key in the subtree rooted at x greater than or equal to the given key
    private Node ceiling(Node x, Key key) {
        if (x == null) {
            return null;
        }
        int cmp = key.compareTo(x.key);
        if (cmp == 0) {
            return x;
        }
        if (cmp > 0) {
            return ceiling(x.right, key);
        }
        Node t = ceiling(x.left, key);
        if (t != null) {
            return t;
        } else {
            return x;
        }
    }

    /**
     * Return the key in the symbol table of a given {@code rank}.
     * This key has the property that there are {@code rank} keys in
     * the symbol table that are smaller. In other words, this key is the
     * ({@code rank}+1)st smallest key in the symbol table.
     *
     * @param rank the order statistic
     * @return the key in the symbol table of given {@code rank}
     * @throws IllegalArgumentException unless {@code rank} is between 0 and
     *                                  <em>n</em>–1
     */
    public Key select(int rank) {
        if (rank < 0 || rank >= size()) {
            throw new IllegalArgumentException("argument to select() is invalid: " + rank);
        }
        return select(root, rank);
    }

    // Return key in BST rooted at x of given rank.
    // Precondition: rank is in legal range.
    private Key select(Node x, int rank) {
        if (x == null) {
            return null;
        }
        int leftSize = size(x.left);
        if (leftSize > rank) {
            return select(x.left, rank);
        } else if (leftSize < rank) {
            return select(x.right, rank - leftSize - 1);
        } else {
            return x.key;
        }
    }

    /**
     * Return the number of keys in the symbol table strictly less than {@code key}.
     *
     * @param key the key
     * @return the number of keys in the symbol table strictly less than {@code key}
     * @throws IllegalArgumentException if {@code key} is {@code null}
     */
    public int rank(Key key) {
        if (key == null) {
            throw new IllegalArgumentException("argument to rank() is null");
        }
        return rank(key, root);
    }

    // number of keys less than key in the subtree rooted at x
    private int rank(Key key, Node x) {
        if (x == null) {
            return 0;
        }
        int cmp = key.compareTo(x.key);
        if (cmp < 0) {
            return rank(key, x.left);
        } else if (cmp > 0) {
            return 1 + size(x.left) + rank(key, x.right);
        } else {
            return size(x.left);
        }
    }

    /***************************************************************************
     *  Range count and range search.
     ***************************************************************************/

    /**
     * 返回所有的key值
     *
     * @return all keys in the symbol table as an {@code Iterable}
     */
    public Iterable<Key> keys() {
        if (isEmpty()) {
            return new Queue<Key>();
        }
        return keys(min(), max());
    }

    /**
     * Returns all keys in the symbol table in the given range,
     * as an {@code Iterable}.
     *
     * @param lo minimum endpoint
     * @param hi maximum endpoint
     * @return all keys in the symbol table between {@code lo}
     * (inclusive) and {@code hi} (inclusive) as an {@code Iterable}
     * @throws IllegalArgumentException if either {@code lo} or {@code hi}
     *                                  is {@code null}
     */
    public Iterable<Key> keys(Key lo, Key hi) {
        if (lo == null) {
            throw new IllegalArgumentException("first argument to keys() is null");
        }
        if (hi == null) {
            throw new IllegalArgumentException("second argument to keys() is null");
        }

        Queue<Key> queue = new Queue<Key>();
        // if (isEmpty() || lo.compareTo(hi) > 0) return queue;
        keys(root, queue, lo, hi);
        return queue;
    }

    // add the keys between lo and hi in the subtree rooted at x
    // to the queue
    private void keys(Node x, Queue<Key> queue, Key lo, Key hi) {
        if (x == null) {
            return;
        }
        int cmplo = lo.compareTo(x.key);
        int cmphi = hi.compareTo(x.key);
        if (cmplo < 0) {
            keys(x.left, queue, lo, hi);
        }
        if (cmplo <= 0 && cmphi >= 0) {
            queue.enqueue(x.key);
        }
        if (cmphi > 0) {
            keys(x.right, queue, lo, hi);
        }
    }

    /**
     * 从新计算元素数量
     *
     * @param lo minimum endpoint
     * @param hi maximum endpoint
     * @return the number of keys in the symbol table between {@code lo}
     * (inclusive) and {@code hi} (inclusive)
     * @throws IllegalArgumentException if either {@code lo} or {@code hi}
     *                                  is {@code null}
     */
    public int size(Key lo, Key hi) {
        if (lo == null) {
            throw new IllegalArgumentException("first argument to size() is null");
        }
        if (hi == null) {
            throw new IllegalArgumentException("second argument to size() is null");
        }

        if (lo.compareTo(hi) > 0) {
            return 0;
        }
        if (contains(hi)) {
            return rank(hi) - rank(lo) + 1;
        } else {
            return rank(hi) - rank(lo);
        }
    }


    /***************************************************************************
     *  Check integrity of red-black tree data structure.
     ***************************************************************************/
    private boolean check() {
        if (!isBST()) {
            System.out.println("Not in symmetric order");
        }
        if (!isSizeConsistent()) {
            System.out.println("Subtree counts not consistent");
        }
        if (!isRankConsistent()) {
            System.out.println("Ranks not consistent");
        }
        if (!is23()) {
            System.out.println("Not a 2-3 tree");
        }
        if (!isBalanced()) {
            System.out.println("Not balanced");
        }
        return isBST() && isSizeConsistent() && isRankConsistent() && is23() && isBalanced();
    }

    // does this binary tree satisfy symmetric order?
    // Note: this test also ensures that data structure is a binary tree since order is strict
    private boolean isBST() {
        return isBST(root, null, null);
    }

    //校验是否为完美平衡查找树
    private boolean isBST(Node x, Key min, Key max) {
        if (x == null) {
            return true;
        }
        if (min != null && x.key.compareTo(min) <= 0) {
            return false;
        }
        if (max != null && x.key.compareTo(max) >= 0) {
            return false;
        }
        return isBST(x.left, min, x.key) && isBST(x.right, x.key, max);
    }

    // are the size fields correct?
    private boolean isSizeConsistent() {
        return isSizeConsistent(root);
    }

    private boolean isSizeConsistent(Node x) {
        if (x == null) {
            return true;
        }
        if (x.size != size(x.left) + size(x.right) + 1) {
            return false;
        }
        return isSizeConsistent(x.left) && isSizeConsistent(x.right);
    }

    // check that ranks are consistent
    private boolean isRankConsistent() {
        for (int i = 0; i < size(); i++) {
            if (i != rank(select(i))) {
                return false;
            }
        }
        for (Key key : keys()) {
            if (key.compareTo(select(rank(key))) != 0) {
                return false;
            }
        }
        return true;
    }

    // Does the tree have no red right links, and at most one (left)
    // red links in a row on any path?
    private boolean is23() {
        return is23(root);
    }

    private boolean is23(Node x) {
        if (x == null) {
            return true;
        }
        if (isRed(x.right)) {
            return false;
        }
        if (x != root && isRed(x) && isRed(x.left)) {
            return false;
        }
        return is23(x.left) && is23(x.right);
    }

    // do all paths from root to leaf have same number of black edges?
    private boolean isBalanced() {
        int black = 0;     // number of black links on path from root to min
        Node x = root;
        while (x != null) {
            if (!isRed(x)) {
                black++;
            }
            x = x.left;
        }
        return isBalanced(root, black);
    }

    // does every path from the root to a leaf have the given number of black links?
    private boolean isBalanced(Node x, int black) {
        if (x == null) {
            return black == 0;
        }
        if (!isRed(x)) {
            black--;
        }
        return isBalanced(x.left, black) && isBalanced(x.right, black);
    }
}

